MNI-normalized images of group-averaged (N = 7) whole brain resting cerebral blood flow (ml/100g/min).

<p>Each session displayed, session 1(S1), session 2 (S2), and session 3 (S3), was the average of runs 1 and 2. Axial slice numbers (Z) in MNI co-ordinates are displayed at the bottom.</p

Blood_tracer_kinetics_in_the_arterial_tree

Blood_tracer_kinetics_in_the_arterial_tre

Voxel-wise whole brain average within-subject coefficient of variance (wsCV) maps calculated for absolute CBF (aCBF) and CBF normalized by grey matter CBF (rCBF).

<p>(A) within-session aCBF, (B) between-session aCBF, (C) within-session rCBF, and (D) between-session rCBF. Histograms were generated from each wsCV map.</p

Representative sample of regional CBF changes associated with finger tapping overlaid on a T1-weighted MNI template brain.

<p>Activation maps were generated for: (a) within-session aCBF images, (b) rest and task aCBF images separated by a week and (c) aCBF images separated by a month, (d) rCBF images separated by a week and (e) rCBF images separated by a month. Regions in colour represent voxels that survived the statistical threshold after correction for family wise error (p < .05, FWE).</p

Mean (± standard deviation) voxel-wise within and between-session: (A) wsCV and (B) ICC value for aCBF and rCBF images in select ROIs.

<p>Mean (± standard deviation) voxel-wise within and between-session: (A) wsCV and (B) ICC value for aCBF and rCBF images in select ROIs.</p

There are two different measures for the tracer concentration in a laminar flow: a) Either by determining the fraction of the labeled volume (black) in the infinitesimal measurement volume near <i>x</i> = <i>x_m</i> at one time instant (snapshot-type) or b) by determining the amount of labeled (black) and non-labeled fluid which has passed a cross section in an infinitesimal time interval [<i>t</i>₁,<i>t</i>₂] and is mixed afterwards (flow-type).

<p>In the first case, all laminae contribute with equal weights, whereas in the latter they are weighted with their corresponding velocities, such that the two measurement types lead to different results.</p

Vascular tree model: The individual segments are considered as straight cylindrical tubes with rigid walls.

<p>The bifurcations are treated symmetric on average as discussed in the text. Within this approximation, the present Weibel's generation numbers <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109230#pone.0109230-Weibel1" target="_blank">[48]</a>, are equivalent to the Horton – Strahler's order numbers <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109230#pone.0109230-Horton1" target="_blank">[49]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109230#pone.0109230-Strahler1" target="_blank">[50]</a> up to the reversed order. Tracer transport from the location <i>a</i> in the stem segment to a location <i>b</i> is described by Eq. 2 with <i>N</i> = 4 in this example.</p

ASL Model (without T₁ relaxtion correction): Concentration time curves at 4 different positions in the vascular tree.

<p>The evolution of the ASL bolus from the labeling region A to a measurement volume V is given with the convolution chain , where is the ASL bolus (1), the are the vessel segment lengths and is the distance from the bifurcation in the last segment (4). The shape of (2,3) is actually defined by the time constants .</p

Fitted maximal velocity, , in the internal carotid artery and for different models (arbitrary units on common scale).

<p>The Gamma-variate model does not include as a parameter.</p><p>Fitted maximal velocity, , in the internal carotid artery and for different models (arbitrary units on common scale).</p

First moment of ASL bolus vs arterial track length for the left and right hemisphere (colors from Fig. 3).

<p>Note that the prediction from theory (solid line) is not a fit in this representation but was determined from the optimal <i>v</i>₀ for the proposed model (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109230#pone-0109230-t001" target="_blank">Table 1</a>). The mixing at bifurcations is reflected in the sawtooth structure of the line.</p